Circulating turbulent fluidized bed regime on flow regime diagram

Abstract

Circulating turbulent fluidized bed (CTFB) regime was recently found under a low superficial gas velocity (Ug) system and contained the advantages of both a conventional turbulent fluidized bed, with an excellent mixing property between the gas and solid phases due to the high solid volume fraction (SVF), and a fast fluidized bed (FFB) or circulating fluidized bed (CFB) regime, which could be employed in a continuous mode. To observe the new flow regime, it was conducted in a plexiglas two-dimensional CFB reactor with a riser of 2.00 m height, 0.15 m width and 0.05 m depth. The interpretation of the SVF profiles along the riser height were used to determine the appearance the tubulent bed front where the turbulent bed was terminated. The identification of the CTFB was a profile without the appearance of a bed front in the riser. In conclusion, the development of a CTFB regime was caused by the turbulent bed expansion, which was affected by the magnitude of Ug. There were three important criteria to perform a CTFB: a solid recirculating rate of at least 300 kg/m2.s, the regulated Ug should be between a bubbling fluidized bed (Uc) and FFB (Utr), and lastly, the most important design parameter, the riser height must be shorter than the maximum turbulent bed expansion, which depends on the choice of solid particles. The functions that showed a good agreement with the experimental results were applied to obtain the correlations that later became the compulsory part of addressing the boundaries for each fluidized bed regime. The advantage of the new flow regime diagram was that it included the aspects of operation and design if CTFB was the desire.